1. Field of the Invention
The present invention relates to a plasma etching apparatus, and more particularly, to a plasma etching apparatus that employs dielectric barrier discharge (DBD) or high pressure capacitively coupled plasma (CCP) discharge to remove a film material in an edge region of a substrate.
2. Description of the Related Art
A method of fabricating semiconductor devices or liquid crystal display devices comprises a process of depositing a plurality of thin films and a process of patterning the films by means of etching.
In general, the deposition and etching of the film are performed in a chamber. In a state where a substrate is seated on the top of a substrate support in the chamber, a reaction gas, a source gas and the like are supplied into the chamber so that a thin film can be deposited on the substrate. At this time, as shown in FIG. 1, the thin film partially remains on upper, side and lower portions of edge regions (see, regions designated by “A” in FIG. 1) of the substrate 10. Accordingly, the portions of the thin film formed on the edge regions of the substrate should be removed.
However, a conventional method of etching a substrate is carried out by using a variety of chemicals. The chemicals involve disadvantages of an adverse effect on the environment and difficulty in local cleaning thereof. Accordingly, new etching methods have been actively studied and applied in practice. One of new etching methods is to use plasma.
Here, plasma refers to ionized gas that is composed of ions, electrons, radicals and the like. This plasma is generated at an ultra-high temperature, a strong electric field, or a high-frequency electromagnetic field.
In particular, the generation of plasma through a glow discharge is achieved by free electrons excited under a direct current or a high-frequency electromagnetic field. The excited free electrons collide with gas molecules to produce an active group such as ions, radicals and electrons. This active group physically and chemically affects the surface of a material, thereby changing the characteristics of the surface. Methods for etching a substrate using plasma can be classified according to pressure in an area where a plasma state is established in a chamber.
In the related art, a glow discharge plasma is generated at low pressure that approximates vacuum. A conventional low-pressure plasma etching apparatus is disclosed in Korean Patent Laid-Open Publication No. 2002-80955. In the conventional low-pressure plasma etching apparatus, an insulator is disposed on the top of a substrate support to face a wafer that will be seated thereon, and an electrode for generating plasma is disposed at an outer periphery of the substrate support and insulator to generate plasma only at an edge region of the wafer, thereby cleaning the edge region of the wafer. In order to generate plasma at low pressure in the conventional plasma etching apparatus, the process should be performed in a low-pressure state, i.e., airtight vacuum state. Accordingly, expensive equipment such as a vacuum chamber, a vacuum exhaust system and the like is required, and the complicated inner configuration of the apparatus causes a problem in that a great deal of time is required for maintenance of the apparatus and vacuum pumping. Furthermore, there is a problem in that it is difficult to apply the apparatus to consecutive processes performed at approximately atmospheric pressure.